Displaying the CGAUX ensign on a member owned vessel.

Per Chapter 3 of the Auxiliary Operations Policy Manual, COMDTINST M16798.3 (series), Auxiliarists may fly the Auxiliary Ensign on operational surface facilities and non-operational surface facilities that display a current facility decal. Those Auxiliarists may fly the Auxiliary Ensign day and night. However, while underway, an Auxiliarist must be onboard when flying the Auxiliary Ensign. 

Auxiliarists must fly the Auxiliary Ensign from the main truck, if the boat has a mast. If there is no mast, Auxiliarists may fly the Auxiliary Ensign from the bow staff, or, if equipped with a radio antenna, from the antenna at a point approximately two-thirds the height of the antenna. Auxiliarists must never fly the Auxiliary Ensign at the stern, so as not to confuse it as a flag of nationality.

Certified Auxiliary land facilities may display the blue Auxiliary Ensign at their base location. The Ensign may only be displayed during the time that the location or facility is in service.

Auxiliary Ensigns are available from the Auxiliary Center (AUXCEN) or District Material Centers in five standard sizes. Dimensions of the Auxiliary Ensign flying on a boat may not exceed those of the National Ensign flown at the same time.  Table 3-1 of the referenced instruction provides the proper Auxiliary Ensign size in relation to boat length.